System for lining large diameter bore holes



Dec. 27, 1966 R. L. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5Sheets-Sheet 1 HHH ml F761 W INVENTORJ IPOBERTLZOOFBOUROW BYJbHN/fE/VRYJ'Cfl/PKE ATTORNEY! Dec. 27, 1966 R. LOOFBOURCSW ETAL3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES INVENTORS RoaERrLLaaFsoz/RowBY JOHN HENRYJcH/PKE AT TORNE Y6 1966 R. 1.. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5Sheets-Sheet 3 1 F/GZA IN VE N TOR) RwERrLlaoFaw/Raw BYJaH/vh'En/RrJbfl/PKE A T TORNE Yo Dec. 27, 1966 R. LOOFBOUROW ETAL 3,

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Filed May 27, 1963 5Sheets-Sheet 4 IN VENTORS koafkrLloofaoz/fiow BY JbH/v/YEn/RYJcn/PKEATraR/vE YJ R. 1.. LOOFBOUROW ETAL 3,293,865

SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Dec. 27, 1966 5 Sheets-Sheet5 Filed May 27, 1963 WE MW Mum MY m E H m United States Patent 3,293,865SYSTEM FOR LINING LARGE DIAMETER BORE HOLES Robert L. Loofbourow, 4032Queen Ave., S., Minneapolis, Minn. 55410, and John Henry Schipke, 5324Lyndale Ave., S., Minneapolis, Minn. 55419 Filed May 27, 1963, Ser. No.283,405 8 Claims. (Cl. 61-41) This invention is directed to the lining,or drilling and lining, of deep bore holes of large diameter extendinginto the earth. More particularly, this invention is directed to thelining of deep large diameter bore holes by means of a rigid tighttubular liner of reinforced settable material cast in stationary slipforms held in place at the surface of the earth over the bore hole, theliner then being lowered into the bore hole as fast as the liner isformed.

It is usual practice to support the walls of wells and similar shaftswith steel casing, successive lengths of casing being made up inthreaded joints or welded as the casing is lowered into the hole. Thecasing is subsequently set in cement which is placed under a hydrostaticpressure greater than the pressure of ground water so that cement slurryenters and seals any water channels in the formation through which thehole passes. While this system is practicable for small diameter holes,the diificulty of using the same materials and methods for larger boreholes and shafts becomes obvious. One need only consider the necessarythickness of such steel liners in order to resist collapse in handlingand while they are being cemented in place. The expense ofmanufacturing, shipping and storing such large and heavy liner sectionspresents a formidable problem.

The present invention contemplates the lining of such large diameterdeep bore holes by means of a continuous tubular reinforced liner whichis cast in stationary slip forms and then lowered into the hole. Bylarge diameter bore holes is meant shafts or holes more than about threeor four feet in diameter. Such holes may be anywhere from severalhundred to several thousand feet in depth. The art of rotary drillinghas developed to the point where shafts of 25 feet in diameter and 1,600feet in depth have been completed. The development of equipment to borelarge daimeter holes and the use of muds to support them temporarilywere ahead of the ability to line such holes when completed, until thetime the present invention was made.

The shaft lining system according to the present invention may beutilized in lining previously formed large diameter bore holes or it maybe utilized to line such a bore hole simultaneously with the drilling ofthe bore hole. In this latter instance the weight of the liner itselfmay be utilized to exert drilling force against the drilling apparatusat the bottom of the hole.

The present invention is illustrated by means of the accompanyingdrawings in which the same numerals are used to identify correspondingparts and in which:

FIGURE 1 is a schematic cross-sectional view of the surface end of adeep large diameter hole bored into the earth and showing means for thecasting of a continuous liner in stationary slip forms;

FIGURE 1A is a similar cross-sectional view showing alternativeexpedients for carrying out the lining system according to theinvention;

FIGURE 2 is a further schematic cross-sectional view of a large diameterhole bored itno the earth and showing means for forming a reinforcedliner in sections by casting in stationary slip forms and then loweringin sections into the hole;

FIGURE 2A is an enlarged fragmentary section of a portion of concreteliner showing means of horizontal reinforcement;

FIGURE 3 is a partial cross-sectional view showing a rotary bit fordrilling large diameter bore holes utilizing the Weight of a slip formedcast concrete liner, shown in drilling position; and,

FIGURE 4 is a partial cross-sectional view of a rotary bit as in FIGURE3 shown in hoisting position with the outermost cutting elementsretracted.

Referring to FIGURE 1 of the drawings, there is shown a large diameterbore hole or shaft 10 extending into the earth. The upper end orforeshaft of the bore hole or shaft 10 adjacent the surface of the earth11 is of somewhat larger diameter and is provided with a cylindricallining 12 extending a short distance into the earth. The usual derrick13 extends above the collar of the shaft. A stationary tubular slip formcomposed of outer Wall 14 and spaced apart inner wall 15 is rigidlysupported at the collar of the shaft. example, from an annular beam 16and suitable bracing. The inner slip form wall 15 may be supported froma platform 17 above the collar of the shaft on the derrick.

An annular unobstructed space 18, which is open at both ends, is definedby the surfaces of slip form walls 14 and 15. The reinforced liner 19 iscast in the stationary slip form by placing a concrete mix or othersettable material into the annular space 18, permitting this to setsufiiciently to retain its form and then discharging from the annularspace at the bottom of the slip form.

In order to form the initial segment of the liner 19, it is necessary totemporarily close the bottom of the stationary slip form in order toretain the initial material poured into the annular space 18 at the topof the slip form. This temporary closure may be in the form of a flangedannular ring 20. This ring is initially supported (as, for example, bythe vertical reinforcing elements) in contact with the bottom edges ofthe slip form walls 14 and 15 to form a temporary bottom closure for theannular space between the walls. Alternatively, ring 20 may be supportedby attaching it to a flanged bell form bulkhead 21 provided with aneyelet 22 by means of which it may be suspended by cable 23.

Both supporting means may be used together. Cable 23, as shown, issuspended from the hook 24 of a hoist means including a pulley block 25suspended by cables 26 from a bank of sheaves 27 at the .top of thederrick. Cable 23 passes through guide means 28 on platform 17 toposition it centrally within the liner.

Ring 26' performs a further function as an anchoring means for verticalreinforcing elements within the cast lining 19. In its preferred form,each reinforcing element is an elongated steel wire or cable 29. Thefree end of reinforcing cable 29 is secured to ring 20. The reinforcingelement extends through the annular space 18 between the walls 14 and 15of the stationary slip form being supplied from a supply reel 30 andthen passing over a sheave 31 supported by the derrick over the annularspace of the stationary slip form. Interconnected reinforcing rods mayalso be used. A plurality of vertical reinforcing elements are providedat relatively uniformly spaced intervals around the periphery of thestationary slip form. Each vertical reinforcing element is preferablyengaged by a jack 32 which serves to maintain the reinforcing elementunder tension, to regulate its rate of feed into the slip form and, insome instances, to support the cast liner.

The inside surfaces of the slip form walls 14 and 15 defining theannular space 18 are smooth so as not to obstruct flow of the linerthrough the form. The initial segment of the prestressed reinforcedliner 19 is formed by placing a suitable concrete mix or other settablematerial into the top of the annulus 18 and substantially filling theform. -The reinforcing elements 29 are preferably The outer wall 14 issupported, for

maintained under tension and spaced from the slip form walls as theconcrete mix is being placed. A relatively quick setting concrete mix ispreferably employed, although resinous materials such as epoxies,polyesters and the like may be used.

The outside diameter of the stationary slip form may range from 3 feetto 25 feet or more and the thickness of the liner formed may range fromseveral inches to a foot and a half or more. form may range from about 4feet to 8 feet or more. The rate of fill of the stationary slip form andthe setting rate of the liner are preferably so interrelated that as theslip form begins to fill up the material placed in the bottom of theslip form has already set sufficiently to retain its form. Thus, beforethe slip form becomes full, the ring 20 may be lowered away from thebottom of the slip form carrying with it the set-up reinforced liner.

The lowering of the ring and liner leaves additional room at the top ofthe slip form to be filled. Thereafter, the cast liner is desirablylowered progressively, either intermittently or continuously, as furthermaterial is progressively added in the top of the slip form. Theprogressive rate at which the liner is formed may vary Widely dependingupon such factors as the diameter of the bore hole, the thickness of theliner, the setting rate and the like. Accordingly, the liner may beprogressively cast and discharged from the stationary slip form at ratesranging from a few inches to several feet per hour.

The movement of the liner through the form simulates hand working of theliner surfaces and results in a relatively impermeable structure.However, Where even greater impermeability is desired, a sealant may beapplied to the outside of the liner as it is formed. Such sealants areknown and include asphaltic paints, sodium silicate, rubber base paints,and the like. One manner of applying a sealant coating is by means of aspray ring 33 disposed below the bottom of the stationary slip form andhaving a plurality of inwardly directed jets or spray nozzles throughwhich a sealant composition is sprayed under pressure. An alternative,or supplementary, method of applying a sealant is to provide a floatinglayer 34 of sealant material in the shaft on top of the drilling liquid35 in the shaft. As the liner is lowered through this floating layer, afilm of sealant is applied to the outer surface of the liner. As theliner is lowered through the drilling liquid the hydrostatic pressureexerted by that column of liquid forces the sealant into the pores ofthe reinforced concrete liner, whether the sealant is applied from thespray means or floating layer, or a combination of the two. The resultis a tightly sealed impermeable dry lined shaft.

The lengthening cast liner is supported and its downward movement iscontrolled by several diflerent means used separately or together. Byclosing the bottom of the liner 19 by a bulkhead 21, the liner is madebuoyant with respect to the drilling liquid 35. The displacement of thedrilling liquid serves both to support the liner and control itsmovement. The liner is also supported by its vertical reinforcingelements which may be fed at a controlled rate either by jack means orby slow speed hoist means. Support is also provided by cable 23 anddownward movement is controlled by connecting this cable to a heavy slowspeed hoist. Where bulkhead 21 is not used, tanks or other containersevacuated of air may be attached to the lower end of the liner toprovide bouyancy.

Referring to FIGURE 1A there is shown schematically a slightly differentarrangement of equipment at the top of a bore hole 10' to be lined. Theforeshaft lining 12' is stepped to provide access for workmen to theslip form cast liner. A derrick structure 13' rests on the collar of theforeshaft lining at the surface of the earth 11'. The stationary tubularslip form composed of outer wall 14' and spaced apart inner wall 15 isrigidly supported near the earths surface above the bore hole. Thereinforced The depth of the stationary slip concrete liner 19 is cast inthe stationary slip form, as

' already generally described. The bottom of the liner 19' is in theform of an annular ring 20'. The liner is both reinforced and supportedby means of a plurality of flexible elongated vertical reinforcingelements 29' anchored in ring 20' and being supplied from a supply reel30' and pasing over a sheave 31' and supported by jack 32'. The reels ofreinforcing elements and the jacks are supported on platform 17' of thederrick 13'. Spray means 33 are provided spaced around the liner 19'below the slip form for application of sealant material.

The slip form walls 14 and 15' are held spaced apart by rigid spreadernumbers 79 spaced at intervals about the periphery of the stationaryslip form. In order to facilitate even distribution of concrete to theslip form, a rotatable distributor means is employed. This includes ahopper 80 mounted on a base 81 which is supported on a platform 82within the stationary slip form. A revolving spout or chute 82distributes the concrete from hopper 80 into the slip form. A lip 83extends around the inner wall 15 of the stationary slip form tofacilitate feeding of the concrete mix from the hopper as the chuterevolves. Concrete mix is sup-plied to the hopper 80 by means of acantilevered conveyor 84. To permit access by workmen to the interior ofthe cast liner 19, a stage 85 is suspended within the liner. This ispreferably by means of a plurality of cables 86 or the like suspendedbelow platform 82. In order to permit access to the staging, a manhole87 is provided in platform 82.

As shown schematically in FIGURE 2, the reinforced concrete liner mayalso be formed in separated segments which are lowered successively intoa shaft and fitted together to form a continuous shaft liner. Referringto FIGURE 2, a hole or shaft 10A of desired depth is bored into theearth. A first liner segment 19A is cast by pouring concrete mix intothe top of a stationary slip form composed of an outer wall 14A and aspaced apart inner wall 15A in the manner already described. This firstformed segment of the reinforced concrete liner is lowered into theshaft and positioned at the bottom of the shaft. Successive segments, asindicated by liner segment 19B, are separately formed and loweredsuccessively into the shaft each being positioned on top of theimmediately preceding lower liner section.

In order to facilitate fitting of the liner segments together, the topof each section is formed with an inward taper and the bottom of eachsection is formed with a mating outward taper. To insure a tight fit anO-ring 40 is preferably also seated in the inward taper at the top ofeach liner section. Then, when the next successive liner section isseated, its weight compresses the O-ring to insure a tight seal.

To protect the liner sections against damage through contact with thewall of the shaft during their passage down through the hole, each linersection is provided with a plurality of centralizers or bumpers 41secured to the outside wall of the liner section and distributed evenlyabout its periphery. These bumpers serve merely to hold the shaft linersections spaced from the wall of the shaft as they are lowered.

The liner sections may be lowered, for example, by means of a cable 23Asecured to eyelets 42 embedded into the top portion of each linersection. Cable 23A passes over a sheave 43 journaled in derrick 13A to ahoist 44. To facilitate gentle lowering of the liner sections, eachliner section is closed at each end by a bottom bulkhead 45 and a topbulkhead 46. Each bulkhead section is lowered through the drillingliquid 35A. The bouyancy of each liner section is controlled by thedensity of the drilling mud, by liquid introduced into the liner insidethe bulkheads and, in some instances, by added weights. A vent hole 47is provided in the upper bulkhead 46 to permit equalization ofpressures.

After all of the liner sections are positioned, the drilling fluid ispumped from the shaft and the bulkheads are removed. The liner sectionsmay be provided with an outer sealant coating either by spraying or bymeans of a floating layer or both, as already described. The bottom ofeach liner section is initially formed by a ring secured to the bottomof the slip form. This ring may either be left in place and lowered aspart of the liner section, or it may be made in sections for removalafter the bottom end of each slip form section has set up sufiicientlyto retain its form.

Although the cast liner is in most instances desirably of a circularcross section, it is by no means so limited. It may be elliptical orrectangular and integral compartmented shaft liners may be case in orderto provide separate channels to accommodate upcast and downcast airmovement. Such a liner may take the form of a compartmented rectangularliner, or a circular compartment inside of a rectangular liner, or arectangular compatment inside of a cicular liner.

The lining system according to the present invention is especiallyadapted to conditions where there is soft wet ground above strong tightbedrock. These conditions make conventional shaft sinking extremelydiflicult. Where these conditions are encountered, the system of thepresent invention is used to extend a tight strong reinforced concreteliner down to a depth at which it may be set tightly into the bedrock. Thereafter, further lining may not be needed because of the strength andtightness of the bedrock. In some areas a succession of wet and dry bedswhich range from loose to coherent are encountered. Where suchconditions are found, the shaft lining system of the present inventionis especially useful to extend a liner which is tight and strong andwhich can be set tightly into bedrock.

The liner produced by casting in stationary slip forms according to thepresent invention may be set in much the same manner as metal casing.The liner may be set in cement grout placed in the liner and displacedinto position by drilling mud pumped after it or, as is more usual incementing large diameter casings, the cement may be placed directly inthe annulus outside the casing. Instead of being set in cement, theliner may be set in a bitumen material. This latter is desirable whereit is contemplated that the ground around the lined shaft might moveas-the result of subsidence expected to accompany mining or otherwise.In this manner water may be completely sealed but the bitumen willadjust plastically to ground movement to maintain the seal rather thancracking.

For additional strength, the liner is also desirably provided withhorizontal reinforcing in the form of rings of appropriate shape tocorrespond to the cross sectional shape of the concrete liner tube andof any desired cross section. In weight and cross section, thesehorizontal reinforcing elements maybe anywhere from light reinforcingrods to heavy rolled structural steel. As shown in FIGURE 2A, arcuaterolled structural steel I-beams 36 are assembled into rings and embeddedin the cast concrete tube. Alternatively, a recessed channel 37 may becast in the Wall of the liner. This is done by inserting a channel forminto the top of the stationary slip forms. This channel form passesthrough the slip form along with the cast concrete tube and may beremoved from the tube after it has cleared the bottom edge of thestationary slip form. Then a ring of structural steel members 36A areinstalled around the liner, set into the recess so as not to protrudeout into the lined shaft. In some instances the reinforcing members 36Bare secured around the cast liner in a cast iron or steel channel 38.

In their simplest form, the horizontal reinforcements are in the form ofrods 39 cast into the concrete. These rods may be wired to the verticalreinforcements 29 if desired. Instead of using a series of horizontalrods, the reinforcements 39 may be in the form of a wire or cable castin the concrete tube in the form of a spiral.

While the reinforcing elements 36A, 36B and 38 are illustrated as beingsecured to the inside periphery of the tube, this is a matter of choiceand they may be installed around the outside periphery. In most cases,however, access to the inside of the cast liner from a stage suspendedfrom the derrick is easier and therefore preferred. These varioushorizontal elements may be used separately or in combination dependentupon the needs dictated by conditions found in any given shaft. Thereinforcing elements may be added uniformly throughout the length of theliner or, where unusual ground pressures are anticipated at particularelevations, additional reinforcement can be added to resist suchpressures.

In order to insure proper alignment of the reinforced concrete tubularliner, concrete should 'be placed evenly around the stationary slipforms. In this manner the tube formed will be straight. A constant checkis maintained on the vertical alignment of the shaft liner in order thatany deviation from vertical can be immediately corrected before itexceeds the predetermined tolerances.

The liner may be cast in the stationary slip form simultaneously withthe drilling operation. In this manner the bore hole is lined virtuallyas fast as it is drilled. When this is done, it is desirable to utilizethe weight of the cast reinforced concrete liner to provide the thrustfor the rotary drilling apparatus. Means for doing this are shown inFIGURES 3 and 4. To bore even moderately hard rock efficiently withrolling cutters requires a large downward force. Ordinarily this issupplied by heavy weights positioned just above the cutters or by thrustcylinders acting against wall jacks.

Referring to FIGURES 3 and 4 there is shown the bottom end of a hole orshaft 10B being drilled. This shaft is lined with a reinforced concreteliner 19C cast in stationary slip forms at the surface and providedaround its periphery with a plurality of centralizers or bumpers 41A. Arotary drilling means is clamped to the bottom end of the liner 19C. Thedrilling means comprises a bit body 50 having an upwardly extendingaxial stem 51 and a downwardly extending pilot stem or stinger 52. Thislatter is engaged by a smaller diameter bore hole 53 to insure alignmentof the bit.

The bit stem 51 rotates within tubular drill stem 54. A clamping ring 55is secured to the lower end of drill stem 54 spaced upwardly from thebottom thereof. The clamping ring 55 has an outer peripheral groove orchannel 56 of substantial width and depth into which is fitted aninflatable resilient tube or ring 57 formed of rubber or the like.Inflatable ring 57, when inflated, serves to clamp the bit meanssecurely to the bottom end of the liner.

The bottom end of drill stem 54 is provided with a flange 58 which bearsagainst the top of the bit body 50. A cutter platform or table 59 in theform of a ring is supported on top of flange 58 for rotation relative tothe drill stem and shaft liner. The cutter table 59 is rotated by one ormore hydraulic motors 60 fitted with pinions 61 engaging a ring gear 62secured to the platform. Thrust is applied to the bit at two points, bythe flange 58 at the bottom of the drill stern and through the motor andpinion to ring gear 62. In order to evenly distribute this thrust, it ispreferred that a plurality of motors and pinions be arrayed uniformlyaround the periphery of the ring gear.

A plurality of small roller cutters 63 are supported under the bit bodyand journaled in brackets 64-67 for rotation as the bit is rotated. Alarge roller cutter 68 which undercuts the bore hole below the end ofliner 19C is journaled for rotation in a pivoted frame or bracket 69.Frame 69 is in the form of a heavy plate pivoted to the bit body by apin 70 and movable in a slot or channel 71 in the bit body. The outerend of slot or channel 71 is considerably wider at 72 to accommodatemovement of the larger roller cutter 68 when the frame 69 is pivotedupwardly, as described hereinafter, for retraction so that the bit maybe hoisted through the liner. In order to impart the rotation of thecutter table 59 to the roller cutters, the bottoin edge of the cuttertable is provided with downwardly depending lugs 73 which engage thelarge cutter frame 69.

In order to permit retraction of the large undercutter, a link means 74is provided. One end of link 74 is pivotally connected at 75 to theframe 69 for the large roller cutter 68. The other end of link 74 ispivotally connected at 76 to a lug on the bottom side of the cuttertable 59.

As shown in FIGURE 4, if for any reason it becomes necessary to retractthe bit, for example, for repair or replacement of parts or the like,the inflatable ring 57 is deflated in order to release the rigidconnection between the bit means and the liner. Then the entire bitstructure may be hoisted up through the liner. As the drill stem 54 isretracted, the clamping ring and associated structure attached to thedrill stem is raised. The cutter table 59 is raised by virtue of flange58 at the bottom of the drill stem. As the cutter table is lifted, forceis exerted through link 74 to cause roller cutter 68 and its frame 69 topivot on the pin 70. Then with the large cutter in this retractedposition the bit may be hoisted up through the liner.

The motor 60 is preferably a mud turbine driven by drilling liquidforced under pressure from the surface. The exhaust from this motormeans is then utilized to carry cuttings from the roller cutters to anannular pan or tray 78 supported on top of the clamping ring and adaptedto be hoisted to the surface and emptied as required. The liquid todrive the motor may be pumped through conduits through the drill stem tothe motor, conveyed through other conduits to the vicinity of the rollercutters and then forced upwardly along with the entrained cuttings fordischarge into the cutting tray A plurality of groups of large and smallcutters are arrayed about the periphery of the bit in order todistribute the thrust and cutting action. While the cutters are shown asif all of their axes lie in a single plane, they are preferablystaggered with respect to one another. While the use of the reinforcedconcrete cast liner to apply thrust to the bit structure is shown withrespect to a specific form of bit, it is to be understood that a numberof different rotary bit means having retractable undercutters are knownand are adaptable for use in conjunction with the liner.

In order to anchor the liner against rotation, some means must beprovided by which the liner may be held. One manner of doing this is tocast flutes or splines in the outside of the liner as it is cast in thestationary slip form at the surface. A ring correspondingly fluted isfixed to the shaft walls near the surface but spaced some distance belowit such that by the time the liner has reached the ring it will haveacquired sufficient strength to withstand shearing off of the flutes orsplines.

As one example of the use of the shaft lining system of the presentinvention, a shaft of 500 foot depth and 20 foot diameter is lined witha cast reinforced concrete tube 16 inches thick. The perimeter of theliner is approximately 63 feet. A total of 95 vertical reinforcing rodsare set around the periphery of the liner spaced approximately 8 inchesapart. The concrete has a weight of about 60 pounds per cubic foot undermud. The reinforcing rods are supported by jacks which carry the weightof the liner until it comes to rest at the bottom of the shaft. Bymultiplying the perimeter of 63 feet by the thickness of 1.33 feet, bythe weight of the concrete of 60 pounds per cubic foot, by the 500 footlength of the liner, the total weight is calculated at approximately2,520,000 pounds or 1,260 tons. This weight is carried by 95 rods andjacks so that each carries 26,500 pounds or 13% tons. This is wellwithin the capacity of available equipment. It must be remembered thatthe bore hole will normally be full of drilling mud whose function is tosupport the walls of the hole until the casing is set. This mud assistsin 8 supporting the liner and the Weight to be supported can be reducedfurther by the use of floats or a bulkhead in the liner or by usingheavy mud and lightweight concrete.

As a further example, a shaft of 20 foot diameter and 1,000 foot depthis provided with a liner having 20 inch thick walls cast in stationaryslip forms using 140 pound per cubic foot concrete. This shaft liner isformed with a water tight bottom bulkhead. The bore hole is filled withdrilling mud having a weight of 75 pounds per cubic foot. The shaft islowered through the mud by adding water to the inside of the concretecasing. At 1,000 feet depth the weight of the shaft liner and the waterinside just balances the 1,000 foot depth of drilling mud outside. Whenthis casing is filled with water, the differential pressure at thebottom results in a compressive unit stress (hoop stress) of only 282pounds per square inch. By proportion we see that concrete feet from thesurface is stressed at 28 pounds per square inch.

Taking another example, a 10 foot diameter shaft having a depth of 1,500feet is lined with a cast concrete tube having 16 inch wall thicknessthroughout. This liner is formed with a bottom bulkhead and is filledwith water as necessary to take the casing down. Using a drilling mud of74 pounds per cubic foot, when the water level inside the casing is 605feet below the surface, the outside pressure is 315 pounds per squareinch and the compressive stress in the wall is 1,500 pounds per squareinch at the water level. The development of adequate compressivestrength in the liner to withstand such stresses presents no problem.

When the vertical reinforcing elements are composed of reels of hightensile strength steel wires, each fed over a head sheave or steel ringdown through adjustable dies to restrain movement of the wire and thenceinto the concrete, the weight which can be supported by each Wire can bereadily calculated and the need for additional support determined. Forexample, Where each wire is of inch diameter and can work at 100,000pounds per square inch, each wire can support about 2,760 pounds.

Similarly, where high strength steel cable, either plain or galvanized,is fed from reels over a ring or sheaves down through cable jacks andinto the concrete, the weight which can be supported by each cable canbe determined. For example, taking galvanized steel bridge strand andassuming a safety factor of two, each 1 inch cable can support 30 tons.

Whether rods, wires, or wire rope are used as the verticalreinforcements, the cylindrical concrete tube is prestressed verticallyby the tension automatically built into this support. This'prestressingbecomes effective as soon as the lower end of the liner rests on theshaft bottom and so supports the weight of the concrete. It binds theconcrete shell together and provides exceptional resistance to anyunequal horizontal stresses.

It is apparent that many modifications and variations of this inventionas hereinbefore set forth may be made without departing from the spiritand scope thereof. The specific embodiments described are given by wayof example only and the invention is limited only by the terms of theappended claims.

We claim:

1. A system for lining a deep large diameter vertical hole bored intothe surface of the earth which comprises casting a reinforced tubularcasing in situ over said hole at the mouth thereof and progressivelylowering said casing as formed into said hole until said hole is linedto the desired depth, said system comprising the steps of:

(A) supporting over the mouth of the hole to be lined tubular verticaluniformly spaced apart stationary forms defining the wall thickness ofsaid casing,

(13) inserting the ends of a plurality of strong continuous metal strandvertical reinforcing elements between said forms uniformly spaced aboutthe pe riphery of the forms from supply sources above the 9 mouth of thehole and anchoring the strands in a removable ring at the bottom of saidforms,

(C) placing concrete -mix between said forms about said reinforcingelements to embed the same,

(D) leaving said concrete mix undisturbed between said forms until setup and hardened into a tubular casing,

(E) lowering said ring from the bottom of said forms a distance lessthan the length of the thusly formed casing segment, at least part ofthe suspended weight of said casing segment being supported by saidreinforcing element to progressively insert further lengths ofreinforcing elements and to maintain the strands thereof under constantsubstantially uniform tension to stress the same, and

(F) progressively placing further concrete into the top of said formsand progressively discharging tubular casing from the bottom thereof ata rate to permit the concrete mix to become set and hardened in thecourse of its passage through the forms.

2. A system according to claim 1 further characterized in that saidcasing is thereafter set in said hole by filling the space between thewall of said hole and the outer wall of said casing with a settablematerial.

3. A system according to claim 1 further characterized in that saidtubular casing is supported in part by drilling liquid in said hole tobe lined as the casing is lowered therein.

4. A system according to claim 3 further characterized in that thebottom end of said casing is closed to render said casing buoyant tofacilitate support thereof by drilling liquid.

5. A system according to claim 1 further characterized in that annularhorizontal reinforcing elements are incorporated in said casing spacedlongitudinally along the length thereof, said horizontal reinforcingelements I being added progressively to said casing as formed.

6. A system according to claim 1 further characterized in that a sealantcoating is applied to the outside of said tubular casing progressivelyas said casing is formed.

7. A system according to claim 6 further characterized in that saidsealant coating is applied to said casing from a layer of sealantmaterial floating on top of drilling liquid disposed in the spacebetween the bore hole wall and easing as the casing passes downwardlythrough the floating layer.

8. A system according to claim 1 further characterized in that saidtubular casing is cast substantially simultaneously along with deepeningof the hole, the weight of the formed casing exerting the thrust forfurther boring.

References Cited by the Examiner UNITED STATES PATENTS 887,952 5/1908Milligan 61-41 X 1,175,952 3/1916 Haase -97 1,574,040 2/1926 Lasher166-24 X 1,847,814 3/1932 Byrne 6141 1,916,686 7/1933 Sandstone 166--242,080,406 5/1937 Allen 166-24 2,706,498 4/1955 Upson 61-56 X FOREIGNPATENTS 729,724 1932 France.

892,734 5/ 1944 France.

257,682 1913 Germany.

1,120,402 12/ 1961 Germany.

CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, Examiner.

C. D. JOHNSON, Assistant Examiner.

1. A SYSTEM FOR LINING A DEEP LARGE DIAMETER VERTICAL HOLE BORED INTOTHE SURFACE OF THE EARTH WHICH COMPRISES CASTING A REINFORCED TUBULARCASING IN SITU OVER SAID HOLE AT THE MOUTH THEREOF AND PROGRESSIVELYLOWERING SAID CASING AS FORMED INTO SAID HOLE UNTIL SAID HOLE IS LINEDTO THE DESIRED DEPTH, SAID SYSTEM COMPRISING THE STEPS OF: (A)SUPPORTING OVER THE MOUTH OF THE HOLE TO BE LINED TUBULAR VERTICALUNIFORMLY SPACED APART STATIONARY FORMS DEFINING THE WALL THICKNESS OFSAID CASING, (B) INSERTING THE ENDS OF A PLURALITY OF STRONG CONTINUOUSMETAL STRAND VERTICAL REINFORCING ELEMENTS BETWEEN SAID FORMS UNIFORMLYSPACED ABOUT THE PERIPHERY OF THE FORMS FROM SUPPLY SOURCES ABOVE THEMOUTH OF THE HOLE AND ANCHORING THE STRANDS IN A REMOVABLE RING AT THEBOTTOM OF SAID FORMS, (C) PLACING CONCRETE MIX BETWEEN SAID FORMS ABOUTSAID REINFORCING ELEMENTS TO EMBED THE SAME, (D) LEAVING SAID CONCRETEMIX UNDISTURBED BETWEEN SAID FORMS UNTIL SET UP AND HARDENED INTO ATUBULAR CASING, (E) LOWERING SAID RING FROM THE BOTTOM OF SAID FORMS ADISTANCE LESS THAN THE LENGTH OF THE THUSLY FORMED CASING SEGMENT, ATLEAST PART OF THE SUSPENDED WEIGHT OF SAID CASING SEGMENT BEINGSUPPORTED BY SAID REINFORCING ELEMENT TO PROGRESSIVELY INSERT FURTHERLENGTHS OF REINFORCING ELEMENTS AND TO MAINTAIN THE STRANDS THEREOFUNDER CONSTANT SUBSTANTIALLY UNIFORM TENSION TO STRESS THE SAME, AND (F)PROGRESSIVELY PLACING FURTHER CONCRETE INTO THE TOP OF SAID FORMS ANDPROGRESSIVELY DISCHARGING TUBULAR CASING FROM THE BOTTOM THEREOF AT ARATE TO PERMIT THE CONCRETE MIX TO BECOME SET AND HARDENED IN THE COURSEOF ITS PASSAGE THROUGH THE FORMS.